Patent GB-1115138-A (GB)
Title: Hydraulic apparatus for controlling at least one hydraulic ram
Inventor: JOHNSON CHRISTOPHER LINLEY
IPC: F02K1/15
Filed: 1966-12-22
Abstract: 1, 115, 138. Hydraulic apparatus; reciprocating pumps; gas turbine jet engines. ROLLS ROYCE Ltd. Dec.22, 1966, No.57582/66. Headings F1A, F1J and F1P. In a gas turbine engine 10, Fig. 1, a nozzle 34 of variable area is controlled by an axially-movable sleeve 31 coupled to a plurality of hydraulic rams 26, each of which rams is connected by pipes 45, 46, Figs. 3 and 4, to inlet and outlet ports 43, 44 of a swash-plate pump 40 that is driven by a shaft 47 coupled to the engine and has its swash-plate 41 connected by a lever 52 to a piston 96 within a control unit 56, which is responsive to pressure changes in the engine so as to effect adjustment of the attitude of the swash-plate and consequently the area of the nozzle 34 accordingly, a diaphragm 171, Fig. 4, being provided to control by-pass passages 164, 165, 166, 174, 175 associated with the pipes 45, 46 to render the rams static and therefore the area of the nozzle constant when the load on said sleeve is increased during a reheating action. The control unit 56 includes a piston 76 carrying a valve-member 77 controlling a passage 81 containing air at atmospheric pressure, the piston being attached to a hollow shaft or stem 74 that slidingly engages with a sleeve 95 carrying a further piston 96. Pipes 67, 85, 94, 99 communicate with a low-pressure portion of a reheat fuel-supply system 23, Fig. 1, the output end of a high-pressure compressor 12, a jet pipe 16 adjacent re-heating fuel-combustion equipment 20, and a high-pressure portion of the system 23, respectively. The sleeve 95 contains passages 111, 112 on either side of the piston 96, which passages are connected by an annular channel or space 105 to a passage 106 in the shaft 74, one or other of the passages 111, 112 being brought into register with a passage 110 at the adjacent end of the passage 105 in accordance with displacement of the piston 76 whenever the ratio of the pressures in the pipes 85, 94 either increases or decreases. Connection of one or other of the spaces on either side of the piston 96 to a chamber 64, to which chamber the pipe 67 is coupled, causes a reduction of pressure in the space concerned and consequently displacement of the piston 96 to effect appropriate alteration of the attitude of the swash-plate 41. The pressure communicated to the piston 76 through the pipe 85 is regulated by a needle valvemember 86 according to the ratio of pressures in spaces 115, 116 on either side of a piston 114, which pressures are one related to the pressure in the pipe 85 and that at the outlet end of a lowpressure compressor 11, Fig. 1, respectively. The piston 114 and an associated piston 121 function in a manner similar to the pistons 76, 96. A linkage system 123, 126, 127, 90 connects the piston 121 to the valve-member 86. Gears 72, 73 that are integral with the shafts 74, 75 mesh with a gear 71 on a rotatable shaft 70, which is driven by the engine, whereby the shafts 74, 75 are rotated to prevent restriction of their axial movement by any foreign matter. The pump 40 includes a backing pump 142 connected to a tank 140 for working fluid, e.g. oil, through a non-return valve 143. Non-return valves 152, 153, 160, 163 are provided between a passage 145 and the pipes 45, 46, as shown, to effect relief of excessive pressures, the passage 145 being connected to said tank through a non-return valve 154. The diaphragm 171 is biased by a spring 173 to a position wherein the passage 165 is open, as shown, pressure being communicated to either side of the diaphragm from the pipes 45, 46, respectively. The pressure difference across the diaphragm is regulated by a needle-valve 181 and reversal of flow from the pipe 46 to the pipe 45, by way of the passage 165, is prevented by a non- return valve 176. A flow-restricting orifice 183 is included in the passage 175 to prevent excessive by-passing of each ram 26. The rate of flow of working fluid through the passage 165 is varied inversely with the output of the pump as a consequence of the deflection of the diaphragm in one direction or the other in response to pressure changes in the pipes 45, 46. Leakage fluid in each ram 26 is returned to the port 43 of the pump 40 through a pipe (190), Fig.5 (not shown), and the tank 140 through a pipe 191, Fig. 4. When the load on the rams 26 is rendered large due to re-heating action, the rate of flow of leakage fluid increases and gives rise to a corresponding increase in the output of the pump 40, which would cause actuation of the rams and an undesirable change in the area of the nozzle 35; but such actuation is prevented by the response of the diaphragm to the change of pressure in the pipes 45, 46 as a consequence of the change in the output of the pump. When the nozzle 35 is adjusted so that its area is minimum, the sleeve 31 moves a valve 205, which controls the rate of flow from the pipe 46 to the pipe 45 through an additional by-pass passage 204, so that said rate of flow is rendered maximum. When the re-heating action is terminated, the pressure of oil in a pipe 132 associated with a piston 133, Fig. 3, is reduced and a further piston 135 attached thereto is displaced by the highpressure in the pipe 99, thereby causing displacement of the shaft 74 by a lever 136 that engages with the gear 72 so as to displace the shaft 74 and effect a change in the attitude of the swashplate 41 in such a manner as to give rise to a reduction in the area of the nozzle 26. A heat-exchanger 193 contains a portion of the pipe 45 so that the working fluid therein is cooled by transference of heat to fuel for the engine passing through ports 195, 196. By-pass passages 200, 201 are controlled by non-return valves 202, 203. The engine includes reheat combustion equipment 20, Fig. 1, which comprises main burners 21 and pilot burners 22 connected to a reheat fuel system 23. A "hot-streak" injector 25 is also connected to the system aforesaid. The nozzle 35 comprises a plurality of members 34, each of which carries a roller 36 that engages with a conical portion 33 of the sleeve 31.